Surfactants reduce the surface tension of water by adsorbing at the liquid-gas interface. They also reduce the interfacial tension between oil and water by adsorbing at the liquid-liquid interface. Surfactants are a primary component of most detergents. When dissolved in water, surfactants give a product the ability to remove soil from surfaces. Each surfactant molecule has a hydrophilic head that is attracted to water molecules and a hydrophobic tail that repels water and simultaneously attaches itself to oil and grease in soil. These opposing forces loosen the soil and suspend it in the water.
Surfactants do the basic work of detergents and cleaning compositions by breaking up stains and keeping the soil in the water solution to prevent re-deposition of the soil onto the surface from which it has just been removed. Surfactants disperse soil that normally does not dissolve in water.
Nonylphenol ethoxylates (NPEs) are predominantly used as industrial and domestic detergents as a surfactant. However, while effective, NPEs are disfavored due to environmental concerns. For example, NPEs are formed through the combination of ethylene oxide with nonylphenol (NP). Both NP and NPEs exhibit estrogen-like properties and may contaminate water, vegetation and marine life. NPE is also not readily biodegradable and remains in the environment or food chain for indefinite time periods.
An alternative to NPEs are alcohol ethoxylates (AEs). These alternatives are less toxic and degrade more quickly in the environment. However, it has recently been found that textiles washed with NPE free and phosphorous free detergents containing AEs smoke when exposed to high heat, e.g., in a steam tunnel in industrial laundry processes, or when ironed.
Surfactants are often incorporated in a cleaning composition to clean soiled surfaces. One of the preferred mechanisms is by microemulsifying these soils. Surfactants are also often incorporated into an oil-in-water microemulsion to make oil containing products appear more homogenous. These oil containing products include a variety of different surfactant systems in 5-20% solubilized oil which may be used as is or which are then diluted with water prior to use. Examples of these oil containing products include cosmetics, products containing oily solvents for degreasing, such as terpene, and other water immiscible solvents. The surfactant systems generally employed in these cleaning products include a mixture of anionic or non-ionic surfactants and a short chain alcohol to help solubilize the oil phase and prevent liquid crystal formation. While short chain alcohols are effective, they also contribute to the volatile organic solvent content (VOC) of the product and pose flammability problems.
As can be seen there is a continuing need to develop effective, environmentally friendly, and safe surfactants and surfactant systems that can be used in cleaners of all kinds. This is particularly so in light of several new cleaning challenges that have emerged.
Health authorities have recently recommended that trans fats be reduced or eliminated in diets because they present health risks. In response, the food industry has largely replaced the use of trans fats with non-trans fats. These types of non-trans fats are the most difficult to remove from surfaces because; 1) the high molecular weight of triglyceride oil results in more difficulty in forming either dispersions or bicontinuous structures, 2) the polyunsaturation of triglyceride oil makes it difficult to be handled by conventional surfactants, and 3) polymerization of the triglyceride oil makes it even more difficult to remove. The food industry and textile cleaning industry have also experienced an unexplained higher frequency of laundry fires. Textile items such as rags that are not effectively washed to better remove non-transfats are prone to cause fire due their substantial heat of polymerization of the trans fats. Non-transfats have conjugated double bonds that can polymerize and the substantial heat of polymerization involved can cause fire, for example, in a pile of rags used to mop up these non-transfat soils.
As can be seen, there is a need in the industry for improvement of cleaning compositions, such as hard surface and laundry detergents and particularly the surfactants used therein so that difficult soils can be removed in a safe environmentally friendly and effective manner.